1. Field of the Invention
The present invention relates to a method of fabricating a thin film transistor substrate, and more particularly to a method of fabricating a thin film transistor substrate that is adaptive for removing a transparent electrode which remains at a non-display area using a contact hole filling process.
2. Description of the Related Art
An image display device has become very important as a visual information communicating media in information society.
A Cathode Ray Tube (CRT), which has been a main stream of the image display device, has problems of heavy weight and bulky volume. There have been developed various flat panel display devices reduced in weight and bulk that is capable of eliminating disadvantages of the cathode ray tube (CRT).
Flat panel display devices include a liquid crystal display device (hereinafter, referred to as “LCD”), a field emission display device (hereinafter, referred to as “FED”), a plasma display panel (hereinafter, referred to as “PDP”), and an electro-luminescence (hereinafter, referred to as “EL”), etc., and most of these flat panel display devices are put to practical use having significant market share in the display device market.
Since the liquid crystal display device satisfies thin profile and light weight of electronics and productivity of the liquid crystal display device is improved, the cathode ray tube has rapidly been replaced with the liquid crystal display device in many application areas.
A liquid crystal display device of active matrix type that drives a liquid crystal cell using a thin film transistor (hereinafter, referred to as “TFT”) has an advantage of an excellent picture quality and a low power consumption, and has been rapidly developed toward a large-dimension screen and a high-resolution by a recent mass-producing technique and the result of a research and development.
A configuration and an operation of the above-mentioned liquid crystal display will be described with reference to FIG. 1 as follows.
A liquid crystal display controls a light transmittance of a liquid crystal using an electric field to display an image. The liquid crystal display includes a thin film transistor, a color filter substrate, a spacer, which is located between two substrates to constantly maintain a cell gap, and a liquid crystal which is filled into the cell gap as shown in FIG. 1.
Herein, a thin film transistor substrate 70 is comprised of a gate line 71 and a data line 72 which are crossed each other, a thin film transistor 73 which is formed at a crossing part of the gate line 71 and the data line 72, a pixel electrode 74 which is connected to the thin film transistor 73, and a lower alignment film (not shown) that aligns a liquid crystal.
In this case, the thin film transistor 73 is comprised of a semiconductor layer that forms a source electrode which is connected to the data line 72, a drain electrode which is opposed to a source electrode with having a channel therebetween, and a channel. Herein, the semiconductor layer includes an active layer that forms a channel between a source electrode and a drain electrode, and an ohmic contact layer which is located on the active layer to make an ohmic contact with a source electrode and a drain electrode.
The color filter substrate 80 is comprised of a black matrix 81 that prevents a light leakage, a color filter 82 that realizes a color, a common electrode 83 that forms a vertical electric field with the pixel electrode 74, and an upper alignment film 84 that is coated for aligning a liquid crystal.
As described above, the thin film transistor substrate is manufactured by a standard mask process, that is, a five mask process or a four mask process, and each mask process is comprised of a lot of processes such as thin film deposition (coating), cleaning, photolithography, etching, photo-resist stripping and inspection processes, etc.
Accordingly, the thin film transistor substrate requires a plurality of mask processes, so that a manufacturing process is complicated, and a manufacturing cost is increased.